Most people are concerned with the degree of pigmentation of their skin. For example, people with age spots or freckles may wish such pigmented spots to be less pronounced. Others may wish to reduce the skin darkening caused by exposure to sunlight or to lighten their natural skin colour. To meet this need, many attempts have been made to develop products that reduce the pigment production in the melanocytes. However, the substances identified thus far tend to have either low efficacy or undesirable side effects, such as, for example, toxicity or skin irritation. Therefore, there is a continuing need for new cosmetic skin lightening agents, with improved overall effectiveness.
Conventional skin lightening compositions are based on use of skin lightening agents that are believed to control dispersion of melanin or inhibit tyrosinase. These skin-lightening agents include niacinamide, carboxylic acids like azelaic acid and kojic acid, plant extracts and hydroquinone etc. Hexylresorcinol, is one such widely used skin lightening agent in compositions for topical application.
The ability of hexylresorcinol to target pathways in the skin that lead to hyperpigmentation has propelled it into the skin lightening ingredient category. It is also thought that hexylresorcinol has more benefits as well, including an ability to reduce the appearance of fine lines and wrinkles, increase protection against UVB and UVA rays, and improve the skin's barrier against pollution and sun exposure.
It has been demonstrated that hexylresorcinol reduces melanin content in melanocytes by its ability to directly inhibit tyrosinase enzyme activity, which in turn is believed to be largely responsible for its ability to provide skin lightening efficacy.
However, a more effective way to reduce melanin content in melanocytes remains to be desired.
US 2002 120225 (McDaniel) discloses a method for enhancing the transport of an active agent through mammalian skin, comprising: exposing the skin to ultrasound, and applying an active agent to the skin, wherein the step of applying an active agent to the skin comprises injecting the active agent into the skin, and wherein the active agent comprises at least one of Vitamin C, Vitamin E, Vitamin A, Vitamin K, Vitamin F, Retin A (Tretinoin), Adapalene, Retinol, Hydroquinone, Kojic acid, a growth factor, echinacea, an antibiotic, an antifungal, an antiviral, a bleaching agent, an alpha hydroxy acid, a beta hydroxy acid, salicylic acid, antioxidant triad compound, a seaweed derivative, a salt water derivative, an antioxidant, a phytoanthocyanin, a phytonutrient, a botanical product, a herbaceous product, a hormone, an enzyme, a mineral, a genetically engineered substance, a cofactor, a catalyst, an antiaging substance, insulin, trace elements, minerals, Rogaine, a hair growth stimulating substance, a hair growth inhibiting substance, a dye, a natural or synthetic melanin, a metalloproteinase inhibitor, proline, hydroxyproline, an anesthetic substance.
It has been found that 4-hexylresorcinol in combination with MMP inhibitor galardin synergistically reduces melanin content in melanocytes. The invention thus relates to a composition comprising a synergistic combination of 4-hexylresorcinol and galardin for use in skin lightening. Thus the composition, when applied topically over an appropriate length of time in-vivo, may be used to lighten the skin, or to reduce age spots or freckles.